An important type of hose of the abovementioned type is a coolant hose. Coolant hoses serve to transport gaseous or liquid coolants, in particular fluorocarbon coolants, in air-conditioning systems, and reference is in particular made in this connection to the following literature: DE 38 20 447 A1; U.S. Pat. No. 5,084,314; DE 42 32 946 A1; U.S. Pat. No. 5,653,475; DE 196 08 318 A1; DE 91 02 495 U1; DE 203 21 380 U1; EP 0 222 323 A1; U.S. Pat. No. 4,905,736; EP 0 826 915 A2; U.S. Pat. Nos. 6,376,036; 5,957,154; and, ATZ Automobiltechnische Zeitschrift 98 (1996) 10, page 541.
Films made of a polymeric material are becoming increasingly important, alongside barrier layers based on resin, for example made of phenolic resin. Monofilms are used here, for example made of a polyamide (PA), as also in particular are multilayer films (film-composite materials), for example made of PA and of a polymer based on ethylene-vinyl alcohol (EVOH).
As far as the internal layer is concerned, materials used are mostly elastomers or thermoplastic elastomers. Further details of the relevant materials technology are provided elsewhere.
Embodiments known hitherto which comply with the most recent requirements relating to compatibility with modern refrigeration lubricants, flexibility, noise attenuation, gas impermeability, and dynamic strength have a braiding material as reinforcement.
The braiding method applies a ply of the yarn-based reinforcement. The braiding machine mostly has respectively 12packages rotating toward the right and toward the left. A package can accept up to eight strands, and up to 96 strands are therefore applied to the hose in one direction, and precisely the same number in the other direction. This process provides a hose with 100% yarn covering. Adhesion between the individual plies, internal layer-yarn-external layer, is produced here via an adhesion promoter, these being present in the polymer mixtures, or via adhesion-promoter solutions applied additionally. This design provides a burst in pressure three times as high as demanded by the standard.
There are also coolant hoses with reinforcement which is not applied by braiding. However, these exhibit reduced pressure resistance and they usually have an intermediate layer made of a polymeric material between the plies of the reinforcement.